The Anatomy of the Spine
There are 24 bones from the top of the spine to the bottom, in three sections. The cervical section includes the neck consisting of 7 cervical vertebrae, the next 12 vertebrae make up the thoracic spine and the lower section of lumbar includes five vertebrae.
Between each vertebra are fibrous fluid-filled capsules called disks that protect the bones by absorbing the shock to the bones from walking, lifting, twisting, sitting, and laying down. When one of these disks is injured, either by trauma or aging, the disk doesn’t actually slip, instead it protrudes or herniates beyond its normal position, often beyond the edges of the vertebra.
Two Types of Slipped Disks
These disks are like a jelly donut, with a soft center surrounded by a tough outer ring. A herniated disk, sometimes called a ruptured disk, is caused by a crack in the outer ring of cartilage that allows the cartilage and some of the soft inner tissue to protrude out of the disk.
A bulging disk affects only the outer layer of cartilage with at least a quarter of the disk’s circumference protruding beyond its normal position. A herniated disk is more likely to cause pain because it protrudes further and irritates nerve roots either by pushing on the nerve or more commonly causing inflammation of the nerve.
Causes of Herniated Disk
There can be many causes of a herniated disk including normal wear and tear, trauma, or injury.
Normal wear and tear occur naturally over a lifetime, impacting the spine and the disks through activities such as standing, sitting, walking, running, and lifting. Over time, the disks degenerate, becoming less elastic and more compressed, resulting in the closing of natural openings of the spine or foramen where the nerves exit the spinal cord to the rest of the body. These exiting nerve roots get pinched, causing significant pain.
Injuries can be traumatic, such as from a car accident, fall, or another event that impacts the spine. Sometimes, however, a herniated disk can occur from a combination of degeneration and injury. As a consequence, something as common as a sneeze can cause a herniated disk.
Signs and Symptoms
Many herniated or bulging disks shown on an MRI image cause no pain. However, when they do, most occur in the lumbar part of the spine, but can also occur in the cervical or thoracic spine. When it occurs, the pain can be sudden or gradually progress over time.
Signs of herniated lumbar disk include arm or leg pain and especially intense pain in the buttocks, thigh, or calf. Herniated cervical disk pain may be most intense in the shoulder and arm and can cause headaches. Pain may shoot into your arm or leg when you cough, sneeze, or move to or from certain positions. Other signs include numbness, tingling, or muscle weakness. Muscle spasms may make you stiff and make standing or straightening limbs difficult.